package server

import (
	"encoding/json"
	"fmt"
	"io"
	"net/http"
	"strings"
	"time"

	"opencode-proxy/internal/proxy"
)

const defaultPort = "6446"
const defaultHost = "127.0.0.1"

// Server is the HTTP server that exposes OpenAI-compatible endpoints.
type Server struct {
	proxy *proxy.Proxy
	port  string
	host  string
	mux   *http.ServeMux
}

// NewServer creates a new Server with the given proxy.
func NewServer(p *proxy.Proxy) *Server {
	s := &Server{
		proxy: p,
		port:  defaultPort,
		host:  defaultHost,
		mux:   http.NewServeMux(),
	}
	s.routes()
	return s
}

// SetPort sets the server port.
func (s *Server) SetPort(port string) { s.port = port }

// SetHost sets the server host.
func (s *Server) SetHost(host string) { s.host = host }

// Port returns the current port.
func (s *Server) Port() string { return s.port }

// Host returns the current host.
func (s *Server) Host() string { return s.host }

func (s *Server) routes() {
	// Catch-all logger first — logs every request we receive
	s.mux.HandleFunc("/", s.logAll)

	s.mux.HandleFunc("GET /health", s.handleHealth)
	s.mux.HandleFunc("GET /v1/models", s.handleModels)
	s.mux.HandleFunc("GET /v1/models/{id}", s.handleModelByID)
	s.mux.HandleFunc("POST /v1/chat/completions", s.handleChatCompletions)
	s.mux.HandleFunc("POST /v1/messages", s.handleMessages)

	// Claude Code appends /v1/messages to ANTHROPIC_BASE_URL automatically.
	// If the user sets ANTHROPIC_BASE_URL=http://...:6446/v1, we get /v1/v1/messages.
	// Fix: also handle the double /v1/v1/messages path.
	s.mux.HandleFunc("POST /v1/v1/messages", s.handleMessages)
}

// logAll captures unmatched requests so we can see what Claude Code is actually hitting.
func (s *Server) logAll(w http.ResponseWriter, r *http.Request) {
	fmt.Printf("[CATCH-ALL] %s %s | Headers: ", r.Method, r.URL.Path)
	for k, v := range r.Header {
		fmt.Printf("%s=%q ", k, v[0])
	}
	fmt.Println()
	w.Header().Set("Content-Type", "application/json")
	w.WriteHeader(http.StatusNotFound)
	fmt.Fprintf(w, `{"error":{"message":"not found: %s %s","type":"not_found"}}`, r.Method, r.URL.Path)
}

// Start begins listening on the configured host:port.
func (s *Server) Start() error {
	addr := fmt.Sprintf("%s:%s", s.host, s.port)
	fmt.Printf("Listening on http://%s\n", addr)
	return http.ListenAndServe(addr, s.mux)
}

// ---------- Auth middleware ----------

// requireAuth returns true if the request has a valid API key.
// If no API key is configured on the proxy, all requests are allowed.
func (s *Server) requireAuth(w http.ResponseWriter, r *http.Request) bool {
	key := s.proxy.APIKey()
	if key == "" {
		return true // no auth required
	}

	// Check Authorization: Bearer <key>
	authHeader := r.Header.Get("Authorization")
	if strings.HasPrefix(authHeader, "Bearer ") {
		if strings.TrimPrefix(authHeader, "Bearer ") == key {
			return true
		}
	}

	// Check x-api-key header
	if r.Header.Get("x-api-key") == key {
		return true
	}

	w.Header().Set("Content-Type", "application/json")
	w.WriteHeader(http.StatusUnauthorized)
	json.NewEncoder(w).Encode(proxy.OpenAIError{
		Error: proxy.OpenAIErrorDetail{
			Message: "Invalid or missing API key. Use Authorization: Bearer <key> or x-api-key header.",
			Type:    "authentication_error",
			Code:    "invalid_api_key",
		},
	})
	return false
}

// ---------- Endpoints ----------

// GET /health
func (s *Server) handleHealth(w http.ResponseWriter, r *http.Request) {
	w.Header().Set("Content-Type", "application/json")
	json.NewEncoder(w).Encode(map[string]any{
		"status":        "ok",
		"version":       "1.0.0",
		"models":        len(s.proxy.Models()),
		"endpoints":     []string{"/v1/chat/completions", "/v1/messages", "/v1/models", "/v1/models/{id}", "/health"},
		"auth_required": s.proxy.APIKey() != "",
	})
}

// GET /v1/models
func (s *Server) handleModels(w http.ResponseWriter, r *http.Request) {
	if !s.requireAuth(w, r) {
		return
	}

	type modelEntry struct {
		ID              string `json:"id"`
		Object          string `json:"object"`
		Created         int64  `json:"created"`
		OwnedBy         string `json:"owned_by"`
		ContextWindow   int    `json:"context_window"`
		MaxOutputTokens int    `json:"max_output_tokens"`
		Description     string `json:"description"`
	}

	models := s.proxy.Models()
	entries := make([]modelEntry, len(models))
	for i, m := range models {
		entries[i] = modelEntry{
			ID:              m.ID,
			Object:          "model",
			Created:         1779000000,
			OwnedBy:         m.OwnedBy,
			ContextWindow:   m.ContextWindow,
			MaxOutputTokens: m.MaxOutputTokens,
			Description:     m.Description,
		}
	}

	w.Header().Set("Content-Type", "application/json")
	json.NewEncoder(w).Encode(map[string]any{
		"object": "list",
		"data":   entries,
	})
}

// GET /v1/models/{id}
func (s *Server) handleModelByID(w http.ResponseWriter, r *http.Request) {
	if !s.requireAuth(w, r) {
		return
	}

	id := r.PathValue("id")
	for _, m := range s.proxy.Models() {
		if m.ID == id {
			w.Header().Set("Content-Type", "application/json")
			json.NewEncoder(w).Encode(map[string]any{
				"id":                m.ID,
				"object":            "model",
				"created":           1779000000,
				"owned_by":          m.OwnedBy,
				"context_window":    m.ContextWindow,
				"max_output_tokens": m.MaxOutputTokens,
				"description":       m.Description,
			})
			return
		}
	}

	writeError(w, http.StatusNotFound, fmt.Sprintf("Model '%s' not found", id), "model_not_found")
}

// POST /v1/chat/completions
func (s *Server) handleChatCompletions(w http.ResponseWriter, r *http.Request) {
	logRequest(r, "chat")
	if !s.requireAuth(w, r) {
		return
	}

	// Read the full body
	body, err := io.ReadAll(r.Body)
	if err != nil {
		writeError(w, http.StatusBadRequest, "Failed to read request body", "invalid_request")
		return
	}
	defer r.Body.Close()

	logBody("chat", body)

	if len(body) == 0 {
		writeError(w, http.StatusBadRequest, "Empty request body", "invalid_request")
		return
	}

	// Forward to upstream
	if err := s.proxy.ForwardChatCompletion(w, r, body); err != nil {
		fmt.Printf("[server] error forwarding request: %v\n", err)
		writeError(w, http.StatusInternalServerError, err.Error(), "proxy_error")
	}
}

// POST /v1/messages — Anthropic Messages API
func (s *Server) handleMessages(w http.ResponseWriter, r *http.Request) {
	logRequest(r, "anthropic")
	if !s.requireAuth(w, r) {
		return
	}

	body, err := io.ReadAll(r.Body)
	if err != nil {
		writeError(w, http.StatusBadRequest, "Failed to read request body", "invalid_request")
		return
	}
	defer r.Body.Close()

	logBody("anthropic", body)

	if len(body) == 0 {
		writeError(w, http.StatusBadRequest, "Empty request body", "invalid_request")
		return
	}

	// Check for Anthropic version header
	av := r.Header.Get("anthropic-version")
	if av != "" {
		fmt.Printf("[anthropic] version: %s\n", av)
	}

	if err := s.proxy.ForwardAnthropicMessages(w, r, body); err != nil {
		fmt.Printf("[server] error forwarding anthropic request: %v\n", err)
		writeError(w, http.StatusInternalServerError, err.Error(), "proxy_error")
	}
}

func logRequest(r *http.Request, kind string) {
	fmt.Printf("[%s] %s %s | Auth=%s | ContentType=%s\n",
		kind, r.Method, r.URL.Path,
		truncate(r.Header.Get("Authorization"), 30),
		r.Header.Get("Content-Type"))
}

func logBody(kind string, body []byte) {
	if len(body) > 500 {
		fmt.Printf("[%s] body (%d bytes): %s...\n", kind, len(body), string(body[:500]))
	} else {
		fmt.Printf("[%s] body: %s\n", kind, string(body))
	}
}

func truncate(s string, maxLen int) string {
	if len(s) > maxLen {
		return s[:maxLen] + "..."
	}
	return s
}

// ---------- Helpers ----------

func writeError(w http.ResponseWriter, status int, message, errType string) {
	w.Header().Set("Content-Type", "application/json")
	w.WriteHeader(status)
	json.NewEncoder(w).Encode(proxy.OpenAIError{
		Error: proxy.OpenAIErrorDetail{
			Message: message,
			Type:    errType,
		},
	})
}

func writeMethodNotAllowed(w http.ResponseWriter, allowed string) {
	w.Header().Set("Content-Type", "application/json")
	w.Header().Set("Allow", allowed)
	w.WriteHeader(http.StatusMethodNotAllowed)
	json.NewEncoder(w).Encode(proxy.OpenAIError{
		Error: proxy.OpenAIErrorDetail{
			Message: fmt.Sprintf("Method not allowed. Use %s.", allowed),
			Type:    "invalid_request_error",
		},
	})
}

// init sets timezone for consistent timestamps
func init() {
	time.Local = time.UTC
}